Glasshouse structures

With a wide variety of uses across commercial horticulture, glasshouses are benefitting from the application of updated technologies, says Sally Drury

Glasshouses: intended to provide best possible environment for the subjects inside - image: Climate Controls/Deforche
Glasshouses: intended to provide best possible environment for the subjects inside - image: Climate Controls/Deforche

Glasshouses have many purposes. Their main function may be production of food crops, bedding and pot plants or flowers. They may be constructed and fitted out with propagation and growing on in mind.

The structures are used as indoor retail areas at garden centres. They can also be designed and built to house plant collections, such as alpines or exotics, and can be used for display. Sometimes glasshouses are constructed purposefully for research. But whether you are a commercial grower, plant raiser, retailer, professional gardener, botanist or research scientist, glasshouses will have one thing in common - they are intended to provide the best possible environment for the subjects inside.

While Venlo houses are the mainstay for commercial production, bays size is now seen as crucial for ease of transport, irrigation and harvesting, while internal features are increasingly sophisticated. For instance, CambridgeHOK recently completed the UK's first commercial-scale 100 per cent LED installation for tomatoes at Wight Salads.

Research facilities

On the research front, the firm has also built a sophisticated vertical farming research centre for lighting company Royal Philips. The GrowWise City Farming Research Center at the High Tech Campus in Eindhoven, the Netherlands, carries out experiments in tailor-made LED lighting, growth and climate recipe combinations for optimum productions models.

It is not unusual for growers to take on and adapt technologies first implemented in research centres. "Plant-based research organisations have always needed to consider both the energy costs and resource use for their research and trials," explains Unigro managing director Keith Hamp. "Historically this has often meant technology has overlapped between the research and commercial industry enabling considerable cost savings. In the current economic climate this is enabling technology developments to transfer from the research arena to the resource-critical world of the production sector."

Unigro, manufacturer of the GroDome, has seen that the horticultural industry has embraced some major technological developments during 2015 and it has been able to contribute in some of the key areas that it believes will impact the future of the industry globally during the next 10 years.

In energy conservation Unigro has designed robust energy-efficient heating and cooling systems to achieve lower costs and a reduced carbon footprint. This has been achieved by incorporating cool and heat sink systems with absorption chiller technology to accomplish major energy reductions and provide secure production or research. Examples can be seen at University of Exeter's Tremough Campus and the University of Warwick.

When it comes to LEDs, both the commercial production and research industries have traditionally been reluctant to change existing lighting products to a new source. However, this has changed for supplementary lighting, resulting in significant running cost benefits. Following the completion of large commercial trials, growers and research facility managers have correspondingly modified their growing programmes to adapt to the new technology, enabling the concerns of the past to be allayed and energy savings to be realised.

LED control system

With its LED partner Phytolux, Unigro has developed an LED control system. Aimed initially for the research sector, it offers advantages in a supplementary lighting environment. For starters, the system boasts the ability to dim sections of lights or individual units almost instantaneously as crop canopy light levels change. Thousands of units can be controlled by local sensors simultaneously with minimal cost and infrastructure implications. The results bring further energy savings and a more uniform light environment.

In addition, LEDs can be adjusted spontaneously without inefficiencies or increased wear. This permits strategies such as "priming" to be practised to ensure that the photosynthetic potential of the plant is maximised and the use of other resources is minimised.

"From a research perspective, our controls development enables the complete manipulation of irradiance in contained environments without natural light," Hamp points out. "Fourteen wavelengths can be manipulated independently to produce a true replication of the fluorescents used for so many years in research without disruption to ongoing works but benefitting from the running cost savings of both lighting and cooling."

There are many ways for both research and commercial production to benefit from Government incentives in the area of sustainable heat production and energy conservation. The Renewable Heat Incentive will be familiar as a way of receiving a 20-year guaranteed income for the generation of renewable heating and, with careful planning and the integration of technologies, the horticultural industry can exploit these opportunities.

Hamp cites an example: "The use of air source heat pumps has the potential to provide a commercial or research estate with a return on investment within three-to-four years as part of a very simple installation. Previously such systems have not been suitable for integration to current systems as problems have been perceived with the transfer of heat from lower-temperature heat-generating systems. However, we have developed a range of fan coil units and control systems that enable such systems to operate well in this application. These systems can be integrated into more complex applications using Unigro in-house software programmes that ensure each application is project specific."

The technology of self-diagnostic controls and continuous efficiency improvements ensure that relatively new technologies for the industry are applied correctly so that they can be exploited rather than made to fit without a proper interface to specific applications. Controls will enable the smaller continuous steps of improvements between the periodic larger leaps for the industry.

"The technology-fuelled development of the horticulture industry offers a very exciting future as various advances in control systems, energy, vertical farming and robotics feature and impact the global industry," says Hamp.

Gardens and estates

Developments also continue in glasshouses for walled gardens and estates. For instance, Hartley Botanic is shortly to launch a new house called the Opus. The Lancashire-based company is well-known for its made-to-measure greenhouse service, traditional orangeries and botanical conservatories. One of its popular structures is the Grand Gallery, from the company's Victorian range. Measuring 8.15m by 4.13m, the house is practical and substantial, and seen as ideal for horticultural institutes.

Hartley Botanic has been exhibiting planted trade stands at the RHS Chelsea Flower Show for close on 60 years but this year managing director Johnny Mobasher will take the firm's presence at the show to a new level with a Main Avenue show garden designed by Catherine MacDonald from Landform Consultants.

The inspiration for the feature glasshouse, which will appear to be emerging from a pool, came from a design by Thomas Heatherwick, one of Britain's most gifted and imaginative designers. The plan is to deliver a garden that celebrates the best of British engineering innovation and, in particular, the glasshouse structures that for which Hartley Botanic is renowned.

A focal feature will be the brand new Opus, a modern glasshouse in a matt bronze finish that celebrates the company's British-engineered structures in a novel and forward-thinking way and demonstrates their sustainability for contemporary as well as period homes. As soon as the show closes its doors, the garden will be dismantled and donated to the Horatio's Garden at the Queen Elizabeth National Spinal Injuries Unit in Glasgow.

In the garden or estate setting, glasshouses are often required to "fit in" aesthetically while also offering the modern advantages of low maintenance as well as that all-important perfect growing environment. At Cardigan Castle in Wales, family-run Griffin Glasshouses, based in Hampshire, was briefed to create like-for-like replacements to remains of original Victorian structures.

There are more than 844 years of history behind the castle at Cardigan, with Rhys ap Gruffyd, Lord Rhys, moving his court there in 1171 and building the castle in stone. Today - with such an atmosphere of antiquity - designing and constructing a 21st century glasshouse in the castle's kitchen garden is not without its challenges.

"This has been one of the most fascinating and delightful challenges in our 50-year history," says Griffin Glasshouses managing director Linda Lane. "In addition to it looking like the original, it had to be totally modern and maintenance-free."

Stepped and tapered

The glasshouse was completed earlier this year and is a stepped and tapered design measuring just 2m at its narrowest point and widening out to 3.9m. It is 10.2m long and is built against the same brick wall as the original structure. But this is where the similarities end. "Our new version is fitted with growing benches and has electrically operated ventilation and an internal water-harvesting system that collects the rain in an internal tank. The water is hand pumped up for irrigation," Lane explains.

"The finish of the aluminium structure is in pebble grey to match the colour of the castle windows. The glasshouse has typical Victorian style - steep pitches and narrow panes of glass. Maintenance, apart from cleaning the glass, is simply a regular hose down to keep the permanent paint finish fresh."

Cardigan Castle gardener Mark Dellar says: "We are very pleased with the look of the greenhouse. It fits perfectly into this traditional Victorian walled garden."

- Whether you are a commercial grower looking for the latest hi-tech glasshouses fitted with LEDs and sophisticated controllers to aid the production of bumper yields or perfect-quality ornamentals, a researcher wanting to provide exacting conditions for plant experiments or a professional gardener needing a smaller structure as a focal point or display house within a garden, the following Buyers' Guide table will help put you in contact with the major suppliers.

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